I misunderstood you, as this sentence was not clear. Lets try again!

But the enclosure still restarts for a while after the MBP shutdown. And the stops while the HD were restarting to spin.

You are "shutting down" the computer. What I expect normally, is the computer shuts down, and the drives remain on, and one light blinks on each disk for a few seconds, one at a time, until all have "flushed" their cache, then all 4 disks shut down, and the computer completes its shutdown.

At this point, the disks should never spin up again. If they were to, it indicates the thunderbay is getting power and a "start" signal from somewhere. thunderbolt is designed so the disks instantly power down, as soon as the thunderbolt cable signal disappears.

Does this make sense? Can you reexplain what happens in this knowledge?

Once again: the computer is not in SLEEP mode but OFF. You never talk about a possible problem with the enclosure... I found this file for download: OWC-ThunderBay-Updater-190619_2066_01.dmg. How do I know if I need to update the TB4 enclosure?

My guess was the computer may be waking the drives to try to index. Its a guess. Even during sleep the system performs actions at times.

I don't understand your reply... The computer doesn't show any sign of restart process, how would Spolight do something on a powered-off computer?...

I have seen this behavior on a 2019 with Monterey. It is indeed annoying.

I wonder if it is a spotlight issue, or a network access issue. I assume you do not have your machine set to wake for network access?

the other idea is see if this is spotlight. Try disabling spotlight on your external volume and see if that stops this.

Until now the OWC TB4 enclosure was directly connected to the MacBook Pro because I thought a direct link was better than passing through the OWC TB3 dock. I tested using the OWC enclosure on the OWC dock and using OWC dock eject before shutting down the MBP.

But the enclosure still restarts for a while after the MBP shutdown. And the stops while the HD were restarting to spin. Not good...

:-(

When your system sleeps, does it power off for a while, then the drives spin up for a few minutes, then spin down again, repeatedly?

Does it do this regardless of whether the lid is closed or not?

This is macOS doing this, its possible it is indexing (or trying to). Do you have wake for network activity enabled or disabled?

I'm running Big Sur 11.6.1... (MacBook Pro 16", 2019)

I have seen this with the mac on Monterey. Its a bug or something in Monterey. I replicated it with 4 Apple volumes.

Thanks for your reply.

The fact is that the way the enclosure behaves is "strange": as soon as the MBP is off, the enclosure light power turns yellow and OWC TB4 stops... but immediately restart with blue light and fan rotating, as if something that had to be done was not... Then, less than 10 seconds afterwards back to yellow light and stop.

André